1. Field of the Invention
The present invention is generally related to the field of mobile security. More particularly, the present invention is related to a method for exchanging strong encryption keys between mobile devices using alternate data transfer methods in wireless personal area networks (WPAN).
2. Description
For local, short-range, and personal area networks, Bluetooth and the emerging UWB (Ultra-Wide-Band) technologies remain the leading protocols in the market today. It is estimated that there are over one billion Bluetooth-enable handhelds in worldwide use today.
One of the most challenging aspects of short-range radiolink technologies, such as Bluetooth, is security. For example, with Bluetooth, link and encryption keys are derived from a PIN (personal identification number)/passkey code that users, of the devices that are to communicate with one another, must physically/manually enter during device-pairing. With devices that enable entry of the PIN/passkey code via an interface device, such as a keypad, the PIN/passkey code may be a user or manufacturer-selected code that must be entered on the spot. Devices that accept user selected PIN/passkey codes that must be entered on the spot may include, but are not limited to, cell phones and laptop computers. Devices that do not have an interface for changing the PIN/passkey code on the device may have a PIN/passkey that is unchangeable. In other words, the PIN/passkey remains the same and is usually set by the manufacturer. Devices with unchangeable PIN/passkey codes may include, but are not limited to, hands-free headsets and printers.
Often times manufacturers will set the same PIN/passkey on each device of its kind. For example, all hands-free headsets manufactured by XYZ Corporation may all have the PIN 3958, which is not secure because it is known for all XYZ wireless devices of its kind.
The purpose of the PIN/passkey is to enable two or more devices wanting to communicate with one another to discover each other and create an encryption key that enables the devices to join what is called a trusted pair or a trusted piconet. The encryption key is used to protect all of the information that is to be exchanged between the devices. The problem that exists today is that the encryption key is being created over the same channel in which the encryption key is to be used to protect communications between the devices, thereby making it vulnerable for attack. In other words, when there are other devices within communication range of a device having the same PIN/passkey in which communications are not desired, these undesirable devices may derive the encryption key, making the desired communicating devices vulnerable to attack.
Currently, the strength of security for wireless USB (Universal Serial Bus), WLAN (Wireless Local Area Networks), short-range radio networks, and personal area networks, such as, for example, Bluetooth and UWB, is based on the strength (Entropy, randomness, and size) of the PIN/passkey code. The more random and the longer the size of the PIN/passkey code, the stronger the PIN/passkey code. Users of devices in which the user has to enter the PIN/passkey code do not want to enter a PIN/passkey that is long in length, thereby jeopardizing the security of the trusted pair or trusted group. For example, users are more comfortable entering a 4-character or less PIN/passkey, but are very uncomfortable with having to enter a PIN/passkey of a greater length than four digits. In fact, with regards to the typical users of such devices, the shorter the PIN, the better.
Thus, what is needed is a method for enabling an out-of-band communications channel, separate and distinct from the communication channel in which communications between the devices are to be protected, to exchange the encryption key for wireless short-range radio and personal area networks, such as, but not limited to, Bluetooth and UWB. What is further needed is a method for enabling transmission of a longer PIN without requiring the user to enter the PIN.